1. Field of the Invention
The present application relates generally to high temperature atomic layer deposition of oxide thin films. The oxide films may serve, for example, as a dielectric material in a semiconductor device.
2. Description of the Related Art
Atomic layer deposition (ALD) is a self-limiting process, whereby alternated pulses of reaction precursors saturate a substrate surface and leave no more than one monolayer of material per pulse. The deposition conditions and precursors are selected to ensure self-saturating reactions, such that an adsorbed layer in one pulse leaves a surface termination that is non-reactive with the gas phase reactants of the same pulse. A subsequent pulse of different reactants reacts with the previous termination to enable continued deposition. Thus, each cycle of alternated pulses leaves typically less or no more than about one molecular layer of the desired material. The principles of ALD type processes have been presented by T. Suntola, e.g. in the Handbook of Crystal Growth 3, Thin Films and Epitaxy, Part B: Growth Mechanisms and Dynamics, Chapter 14, Atomic Layer Epitaxy, pp. 601-663, Elsevier Science B.V. 1994, the disclosure of which is incorporated herein by reference. Variations of ALD have been proposed that allow for modulation of the growth rate. However, to provide for high conformality and thickness uniformity, these reactions are still more or less self-saturating.
Chemical vapor deposition (CVD) is a process in which atoms or molecules contained in a vapor deposit on a surface to form a film. CVD allows for the growth of films on device surface areas, including “epitaxial” films comprised of a crystalline silicon-containing material. Typically, CVD processes require higher temperatures to initiate reactions. In contrast to ALD, CVD is not a self-limiting process.